In engine block assemblies, a crankshaft converts translational motion of one or more pistons into rotational motion for propelling an on-road vehicle. The crankshaft is retained and supported between thrust surfaces of a cylinder block comprising combustion chambers and main bearing caps. Specifically, the main bearing caps may be bolted to the cylinder block to retain and support the crankshaft. Bearings may be positioned between the thrust surfaces and the crankshaft, and may be lubricated to enable rotation of the crankshaft. Main journals of the crankshaft may directly interface with the bearings. Engine performance and long-term degradation may be affected by circumferential and/or axial profiles of the crankshaft and main bearings. To increase engine performance, and reduce long-term degradation of engine components, one or more of the crankshaft and bearings may be machined to attain a desired axial profile.
However, the inventors herein have recognized potential issues with such systems. Specifically, machining of the crankshaft and/or bearings may be time consuming, expensive, and may be subject to very low error tolerances. Further, machining of the crankshaft and/or bearings may be inconsistent.
As one example, the issues described above may be addressed by an engine block assembly comprising a cylinder block, and a bearing cap bolted to the cylinder block, the bearing cap comprising, a first recess included in a first surface, a second recess included in a second surface opposite the first surface, and a thrust surface interfacing with a crankshaft bearing, where a rigidity of the thrust surface varies along an axial profile of the thrust surface due to the first and second recesses.
The rigidity of the thrust surface may be greater more proximate a central axis of the bearing cap than at edges of the thrust surface. As such, the thrust surface may bend to a more convex axial profile when bolting the bearing cap to the cylinder block. Further, when bolting the bearing cap to the cylinder block, the thrust surface may exert a compressive force on the crankshaft bearing. However, due to the bending of the thrust surface, the compressive force may vary along an axial profile of the bearing, where the compressive force may greater nearer a central axis of the crankshaft bearing. Thus, the bearing may bend such that a convexity of the axial profile of the bearing is increased. As such, machining of the crankshaft and/or bearing may be reduced, and therefore the cost of the engine block assembly may be reduced. Further, the time to produce the engine block assembly may be reduced.
In another example, a crankshaft main bearing cap may comprise a first recess included on a front surface of the bearing cap, a second recess included on a back surface, opposite the front surface, a semicircular thrust surface for retaining a crankshaft, where a flexibility of the thrust surface may vary along an axial profile of the thrust surface, and a thrust bearing adapted to interface with the thrust surface and a main journal of the crankshaft.
In yet another example, an engine block assembly may comprise a cylinder block, a crankshaft, a bearing cap bolted to the cylinder block, the bearing cap comprising a first recess extending inwards from a front first surface of the bearing cap, a second recess extending inwards from a second surface opposite the first surface, and a thrust surface, where a mechanical strength of the thrust surface may be greater nearer a central axis of the thrust surface, and a crankshaft bearing positioned between the crankshaft and the bearing cap, and where a first surface of the bearing may interface with the thrust surface, and where an opposite second surface of the bearing may interface with a main journal of the crankshaft.
In this way, the cost, and time to produce an engine cylinder block assembly may be reduced. Further the consistency of a shape of a main bearing of the engine cylinder block may be increased. By including recesses on main bearing caps of the cylinder block assembly, the compressive force exerted on the bearing caps when the bearing caps are bolted to the cylinder block may vary along an axial profile of the bearings. As such, an axial profile of the bearings may be achieved when bolting the bearing caps to the cylinder block, and therefore expensive and time consuming machining of the bearings and/or crankshaft may be reduced and/or eliminated.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.